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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Precision contact of the fingertip reduces postural sway of individuals with bilateral vestibular loss

Contact of the hand with a stationary surface attenuates postural sway in normal individuals even when the level of force applied is mechanically inadequate to dampen body motion. We studied whether subjects without vestibular function would be able to substitute contact cues from the hand for their lost labyrinthine function and be able to balance as well as normal subjects in the dark without finger contact. We also studied the relative contribution of sight of the test chamber to the two groups. Subjects attempted to maintain a tandem Romberg stance for 25 s under three levels of fingertip contact: no contact; light-touch contact, up to 1 N (approximately 100 g) force; and unrestricted contact force. Both eyes open and eyes closed conditions were evaluated. Without contact, none of the vestibular loss subjects could stand for more than a few seconds in the dark without falling; all the normals could. The vestibular loss subjects were significantly more stable in the dark with light touch of the index finger than the normal subjects in the dark without touch. They also swayed less in the dark with light touch than when permitted sight of the test chamber without touch, and less with sight and touch than just sight. The normal subjects swayed less in the dark with touch than without, and less with sight and touch than sight alone. These findings show that during quiet stance light touch of the index finger with a stationary surface can be as effective or even more so than vestibular function for minimizing postural sway.

NASA Discipline Neuroscience↗
NASA NTRS1993

Vestibular ontogeny: Measuring the influence of the dynamic environment

In comparison to other special senses, we are only meagerly informed about the development of vestibular function and the mechanisms that may operate to control or influence the course of vestibular ontogeny. Perhaps one contributing factor to this disparity is the difficulty of evaluating vestibular sense organs directly and noninvasively. The present report describes a recently developed direct noninvasive vestibular function test that can be used to address many basic questions about the developing vestibular system. More particularly, the test can be used to examine the effects of the dynamic environment (e.g. gravitational field and vibration) on vestibular ontogeny.

Jones, Timothy A.↗
NASA NTRS1984

The Development of the Vestibular Apparatus Under Conditions of Weightlessness

A series of experiments has been carried out on the effect of space flight conditions on morphogenesis and the structure of the vestibular apparatus in amphibian and fish larvae. Larval development proceeded in weightlessness without serious morphological defects. The vestibular apparatus developed; its organization in the experimental animals did not differ qualitatively from that in the controls. The specific external stimulus (gravitation) appears not to be a necessary condition for the development of a gravitation receptor in ontogenesis although the appearance of the vestibular apparatus in phylogenesis was apparently related to this stimulus.

Vinnikov, Y. A.↗
NASA NTRS2016

Functional Imaging of Human Vestibular Cortex Activity Elicited by Skull Tap and Auditory Tone Burst

The current study characterizes brain activation in response to two modes of vestibular stimulation: skull tap and auditory tone burst. The auditory tone burst has been used in previous studies to elicit either the vestibulo-spinal reflex (saccular-mediated colic Vestibular Evoked Myogenic Potentials (cVEMP)), or the ocular muscle response (utricle-mediated ocular VEMP (oVEMP)). Some researchers have reported that air-conducted skull tap elicits both saccular and utricle-mediated VEMPs, while being faster and less irritating for the subjects. However, it is not clear whether the skull tap and auditory tone burst elicit the same pattern of cortical activity. Both forms of stimulation target the otolith response, which provides a measurement of vestibular function independent from semicircular canals. This is of high importance for studying otolith-specific deficits, including gait and balance problems that astronauts experience upon returning to earth. Previous imaging studies have documented activity in the anterior and posterior insula, superior temporal gyrus, inferior parietal lobule, inferior frontal gyrus, and the anterior cingulate cortex in response to different modes of vestibular stimulation. Here we hypothesized that skull taps elicit similar patterns of cortical activity as the auditory tone bursts, and previous vestibular imaging studies. Subjects wore bilateral MR compatible skull tappers and headphones inside the 3T GE scanner, while lying in the supine position, with eyes closed. Subjects received both forms of the stimulation in a counterbalanced fashion. Pneumatically powered skull tappers were placed bilaterally on the cheekbones. The vibration of the cheekbone was transmitted to the vestibular system, resulting in the vestibular cortical response. Auditory tone bursts were also delivered for comparison. To validate our stimulation method, we measured the ocular VEMP outside of the scanner. This measurement showed that both skull tap and auditory tone burst elicited vestibular evoked myogenic potentials, indicated by eye muscle responses. We further assessed subjects' postural control and its correlation with vestibular cortical activity. Our results provide the first evidence of using skull taps to elicit vestibular activity inside the MRI scanner. By conducting conjunction analyses we showed that skull taps elicit the same activation pattern as auditory tone bursts (superior temporal gyrus), and both modes of stimulation activate previously identified vestibular cortical regions. Additionally, we found that skull taps elicit more robust vestibular activity compared to auditory tone bursts, with less reported aversive effects. This further supports that the skull tap could replace auditory tone burst stimulation in clinical interventions and basic science research. Moreover, we observed that greater vestibular activation is associated with better balance control. We showed that not only the quality of balance (indicated by the amount of body sway) but also the ability to maintain balance for a longer time (indicated by the balance time) was associated with individuals' vestibular cortical excitability. Our findings support an association between vestibular cortical activity and individual differences in balance. In sum, we found that the skull tap stimulation results in activation of canonical vestibular cortex, suggesting an equally valid, but more tolerable stimulation method compared to auditory tone bursts. This is of high importance in longitudinal vestibular assessments, in which minimizing aversive effects may contribute to higher protocol adherence.

Noohi, F.↗
NASA NTRS1998

The effect of a BRN 3.1 deletion on the temperature response to 2G

Researchers studied the effect of 2G exposure on body temperature in Wild type and BRN 3.1 Knockout mice to determine the feasibility to using BRN 3.1 Knockout mice as an animal model of the effects of altered gravitational fields on vestibular system physiology.

NASA Discipline Neuroscience↗
NASA NTRS2003

Using Tri-Axial Accelerometers to Assess the Dynamic Control of Head Posture During Gait

Long duration spaceflight is known to cause a variety of biomedical stressors to the astronaut. One of the more functionally destabilizing effects of spaceflight involves microgravity-induced changes in vestibular or balance control. Balance control requires the integration of the vestibular, visual, and proprioceptive systems. In the microgravity environment, the normal gravity vector present on Earth no longer serves as a reference for the balance control system. Therefore, adaptive changes occur to the vestibular system to affect control of body orientation with altered, or non-present, gravity and/or proprioceptive inputs. Upon return to a gravity environment, the vestibular system must re-incorporate the gravity vector and gravity-induced proprioceptive inputs into the balance control regime. The result is often a period of postural instability, which may also be associated with space motion sickness (oscillopsia, nausea, and vertigo). Previous studies by the JSC Neuroscience group have found that returning astronauts often employ alterations in gait mechanics to maintain postural control during gait. It is believed that these gait alterations are meant to decrease the transfer of heel strike shock energy to the head, thus limiting the contradictory head and eye movements that lead to gait instability and motion sickness symptoms. We analyzed pre- and post-spaceflight tri-axial accelerometer data from the NASA/MIR long duration spaceflight missions to assess the heel to head transfer of heel strike shock energy during locomotion. Up to seven gait sessions (three preflight, four postflight) of head and shank (lower leg) accelerometer data was previously collected from six astronauts who engaged in space flights of four to six months duration. In our analysis, the heel to head transmission of shock energy was compared using peak vertical acceleration (a), peak jerk (j) ratio, and relative kinetic energy (a). A host of generalized movement variables was produced in an effort to isolate those that best highlighted vestibular adaptation due to spaceflight. Data suggest that astronauts used either head or body centered control to reduce the effects of heel strike shock on head position during normal walking at self-selected speeds. Moreover, the form of that control appears to fall under one of two categories: homeostatic or adaptive. Homeostatic control refers to tight constraint (small error) over the value of a given variable before and after spaceflight with little or no adaptive changes. Adaptive control refers to lesser constraint over a given movement variable with clear adaptation to earth gravity upon return from spaceflight. Heel strike shock absorption (ratio of heel to head peak acceleration) best-discriminated head and body centered control strategies. Further, peak jerk data was useful for illustrating pre- and postflight differences in segmental (shank versus head) movement energy. Results from kinetic energy analysis show high consistency between subjects and across test dates. Whether this result highlights a control strategy or is an artifact of approximating body segments using anthropometric tables is, at this point, unclear.

Lawrence, John H., III↗
NASA NTRS2005

Development and Function of the Mouse Vestibular System in the Absence of Gravity Perception

The hypothesis that was tested in this research was that the absence of gravity perception, such as would occur in space, would affect the development and function of the vestibular and central nervous systems. Further, we postulated that these effects would be more significant at specific stages of post-natal development of the animal. We also proposed the use of molecular genetic approaches that would provide important information as to the hierarchy of gene function during the development and subsequent function of the vestibular system. The tilted (tlt) mutant mouse has been characterized as lacking the ability to provide sensory input to the gravity receptors. The tlt/tlt mutant mice were a particularly attractive model for the study of vestibular function since the primary defect was limited to the receptor part of the vestibular system, and there were no detectable abnormal phenotypes in other organ systems. The goal of the proposed studies was to assess immediate and delayed effects of the lack of gravity perception on the vestibular system. Particular attention was paid to characterizing primarily affected periods of vestibular morphogenesis, and to identifying downstream genetic pathways that are altered in the CNS of the tlt/tlt mutant mouse. The specific aims were: (1) to characterize the postnatal morphogenesis of the CNS in the tlt mutant mouse, using detailed morphometric analysis of isolated vestibular ganglia and brain tissue at different stages of postnatal development and assessment of apoptotic cell death; (2) to examine the expression of selected genes implicated by mutational analysis to be important in vestibular development or function by in situ hybridization or immunohistochemistry in the mutant mice; and (3) to identify other genes involved in vestibular development and function, using differential cloning strategies to isolate genes whose expression is changed in the mutant versus normal vestibular system.

Wolgemuth, Debra J.↗
NASA NTRS2014

Optimal Stimulus Amplitude for Vestibular Stochastic Stimulation to Improve Sensorimotor Function

Sensorimotor changes such as postural and gait instabilities can affect the functional performance of astronauts when they transition across different gravity environments. We are developing a method, based on stochastic resonance (SR), to enhance information transfer by applying non-zero levels of external noise on the vestibular system (vestibular stochastic resonance, VSR). Our previous work has shown the advantageous effects of VSR in a balance task of standing on an unstable surface. This technique to improve detection of vestibular signals uses a stimulus delivery system that is wearable or portable and provides imperceptibly low levels of white noise-based binaural bipolar electrical stimulation of the vestibular system. The goal of this project is to determine optimal levels of stimulation for SR applications by using a defined vestibular threshold of motion detection. A series of experiments were carried out to determine a robust paradigm to identify a vestibular threshold that can then be used to recommend optimal stimulation levels for SR training applications customized to each crewmember. Customizing stimulus intensity can maximize treatment effects. The amplitude of stimulation to be used in the VSR application has varied across studies in the literature such as 60% of nociceptive stimulus thresholds. We compared subjects' perceptual threshold with that obtained from two measures of body sway. Each test session was 463s long and consisted of several 15s sinusoidal stimuli, at different current amplitudes (0-2 mA), interspersed with 20-20.5s periods of no stimulation. Subjects sat on a chair with their eyes closed and had to report their perception of motion through a joystick. A force plate underneath the chair recorded medio-lateral shear forces and roll moments. First we determined the percent time during stimulation periods for which perception of motion (activity above a pre-defined threshold) was reported using the joystick, and body sway (two standard deviation of the noise level in the baseline measurement) was detected by the sensors. The percentage time at each stimulation level for motion detection was normalized with respect to the largest value and a logistic regression curve fit was applied to these data. The threshold was defined at the 50% probability of motion detection. Comparison of threshold of motion detection obtained from joystick data versus body sway suggests that perceptual thresholds were significantly lower, and were not impacted by system noise. Further, in order to determine optimal stimulation amplitude to improve balance, two sets of experiments were carried out. In the first set of experiments, all subjects received the same level of stimuli and the intensity of optimal performance was projected back on subjects' vestibular threshold curve. In the second set of experiments, on different subjects, stimulation was administered from 20-400% of subjects' vestibular threshold obtained from joystick data. Preliminary results of our study show that, in general, using stimulation amplitudes at 40-60% of perceptual motion threshold improved balance performance significantly compared to control (no stimulation). The amplitude of vestibular stimulation that improved balance function was predominantly in the range of +/- 100 to +/- 400 micro A. We hypothesize that VSR stimulation will act synergistically with sensorimotor adaptability (SA) training to improve adaptability by increasing utilization of vestibular information and therefore will help us to optimize and personalize a SA countermeasure prescription. This combination will help to significantly reduce the number of days required to recover functional performance to preflight levels after long-duration spaceflight.

Goel, R.↗
NASA NTRS2002

Convergence of limb, visceral, and vertical semicircular canal or otolith inputs onto vestibular nucleus neurons

The major goal of this study was to determine the patterns of convergence of non-labyrinthine inputs from the limbs and viscera onto vestibular nucleus neurons receiving signals from vertical semicircular canals or otolith organs. A secondary aim was to ascertain whether the effects of non-labyrinthine inputs on the activity of vestibular nucleus neurons is affected by bilateral peripheral vestibular lesions. The majority (72%) of vestibular nucleus neurons in labyrinth-intact animals whose firing was modulated by vertical rotations responded to electrical stimulation of limb and/or visceral nerves. The activity of even more vestibular nucleus neurons (93%) was affected by limb or visceral nerve stimulation in chronically labyrinthectomized preparations. Some neurons received non-labyrinthine inputs from a variety of peripheral sources, including antagonist muscles acting at the same joint, whereas others received inputs from more limited sources. There was no apparent relationship between the spatial and dynamic properties of a neuron's responses to tilts in vertical planes and the non-labyrinthine inputs that it received. These data suggest that non-labyrinthine inputs elicited during movement will modulate the processing of information by the central vestibular system, and may contribute to the recovery of spontaneous activity of vestibular nucleus neurons following peripheral vestibular lesions. Furthermore, some vestibular nucleus neurons with non-labyrinthine inputs may be activated only during particular behaviors that elicit a specific combination of limb and visceral inputs.

NASA Discipline Developmental Biology↗
NASA NTRS1979

Space motion sickness

Research on the etiology, prediction, treatment and prevention of space motion sickness, designed to minimize the impact of this syndrome which was experienced frequently and with severity by individuals on the Skylab missions, on Space Shuttle crews is reviewed. Theories of the cause of space motion sickness currently under investigation by NASA include sensory conflict, which argues that motion sickness symptoms result from a mismatch between the total pattern of information from the spatial senses and that stored from previous experiences, and fluid shift, based upon the redistribution of bodily fluids that occurs upon continued exposure to weightlessness. Attempts are underway to correlate space motion sickness susceptibility to different provocative environments, vestibular and nonvestibular responses, and the rate of acquisition and length of retention of sensory adaptation. Space motion sickness countermeasures under investigation include various drug combinations, of which the equal combination of promethazine and ephedrine has been found to be as effective as the scopolomine and dexedrine combination, and vestibular adaptation and biofeedback training and autogenic therapy.

Homick, J. L.↗
NASA NTRS1980

Results of the study of the vestibular apparatus and the functions of the perception of space in cosmonauts (pre- and post-flight observations)

The effect of the set of space flight factors caused a change in the activity of the vestibular apparatus and the spatial perception function. More significant and longer shifts were observed during expeditions of great duration. The detected disorders (increase in reactivity of the otolithic apparatus, decrease in sensitivity of the cupula receptor, deterioration in the perception accuracy, etc.) had a definite tendency to be restored. The primary damage to the otolithic reflex (changes were found in practically all the subjects) is probably caused by the specific effect of zero gravitation, and apparently, may be one of the trigger mechanisms for discrepancy in the activity of the sensory systems, disorders in the correcting function of the cerebellum, and central vestibular formations.

Yakovleva, I. Y.↗
NASA NTRS1999

BRN 3.1 Knockouts Affect the Vestibular, Autonomic, and Circadian Rhythm Responses to 2G Exposure

Our previous studies have demonstrated that 2G exposure via centrifugation significantly attenuated the daily mean and circadian rhythm amplitude of rat body temperature (Tb), heart rate, and activity (Act). In addition, 2G exposure activates neural responses in several vestibular, autonomic, and circadian nuclei. Although we have characterized the effect of 2G on an animal's physiological, neuronal, and behavioral responses, it will be important to understand the underlying neural and physiological mechanisms that mediate those responses. For example, the vestibular responses, proprioceptive feedback, or fluid shifts may be the critical factors that mediate the responses to 2G. As a first step to understand the relative importance of these different response pathways to altered gravitational fields, this study examined the contribution of the vestibular system by utilizing an animal model from molecular biology. Brain 3.1 (Bm 3.1) is a POU domain homeobox gene involved in the normal development of the vestibular and auditory system. Brn 3.1 deletion results in a loss of hair cells in the otoliths, semicircular canals, and cochlea. As a result mice with a Brn 3.1 deletion do not have a functioning vestibular or auditory system. The BRN 3.1 knockout mouse could be a very useful animal model for isolating the role of the vestibular system in mediating the physiological responses to 2G exposure. Therefore, this study compared the effect of 2G exposure via centrifugation between Brn 3.1 knockout (KO) versus Wildtype (W) mice.

Murakami, D. M.↗
NASA NTRS2014

Improving Sensorimotor Function Using Stochastic Vestibular Stimulation

Astronauts experience sensorimotor changes during spaceflight, particularly during G-transition phases. Post flight sensorimotor changes may include postural and gait instability, spatial disorientation, and visual performance decrements, all of which can degrade operational capabilities of the astronauts and endanger the crew. Crewmember safety would be improved if these detrimental effects of spaceflight could be mitigated by a sensorimotor countermeasure and even further if adaptation to baseline could be facilitated. The goal of this research is to investigate the potential use of stochastic vestibular stimulation (SVS) as a technology to improve sensorimotor function. We hypothesize that low levels of SVS will improve sensorimotor performance through stochastic resonance (SR). The SR phenomenon occurs when the response of a nonlinear system to a weak input signal is optimized by the application of a particular nonzero level of noise. Two studies have been initiated to investigate the beneficial effects and potential practical usage of SVS. In both studies, electrical vestibular stimulation is applied via electrodes on the mastoid processes using a constant current stimulator. The first study aims to determine the repeatability of the effect of vestibular stimulation on sensorimotor performance and perception in order to better understand the practical use of SVS. The beneficial effect of low levels of SVS on balance performance has been shown in the past. This research uses the same balance task repeated multiple times within a day and across days to study the repeatability of the stimulation effects. The balance test consists of 50 sec trials in which the subject stands with his or her feet together, arms crossed, and eyes closed on compliant foam. Varying levels of SVS, ranging from 0-700 micro A, are applied across different trials. The subject-specific optimal SVS level is that which results in the best balance performance as measured by inertial measurement units placed on the upper and lower torso of the subjects. Additionally, each individual’s threshold for illusory motion perception of suprasensory electrical vestibular stimulation is measured multiple times within and across days to better understand how multiple SVS test methods compare. The second study aims to demonstrate stochastic resonance in the vestibular system using a perception based motion recognition task. This task measures an individual’s velocity threshold of motion recognition using a 6-degree of freedom Stewart platform and a 3-down/1-up staircase procedure. For this study, thresholds are determined using 150 trials in the upright, head-centered roll tilt motion direction at a 0.2 Hz frequency. We aim to demonstrate the characteristic bell shaped curve associated with stochastic resonance with each subject’s motion recognition thresholds at varying SVS levels ranging from 0 to 1500 micro A. The curve includes the individual’s baseline threshold with no SVS, optimal or minimal threshold at some mid-level of SVS, and finally degraded or increased threshold at a high SVS level. An additional aim is to formally retest each subject at his or her individual optimal SVS level on a different day than the original testing for additional validity. The overall purpose of this research is to further quantify the effects of SVS on various sensorimotor tasks and investigate the practical implications of its use in the context of human space flight so that it may be implemented in the future as a component of a comprehensive countermeasure plan for adaptation to G-transitions.

Galvan, R. C.↗
NASA NTRS2002

Maternal susceptibility to nausea and vomiting of pregnancy: is the vestibular system involved?

Nausea and vomiting of pregnancy shares many characteristics with motion sickness, a vestibular dependent phenomenon. A number of physiologic changes that occur in normal pregnancy are also known to accompany nausea and vomiting in patients with motion sickness and certain vestibular disorders. This chapter summarizes some shared features of both phenomena. The unmasking of subclinical vestibular disorders may account for some cases of hyperemesis gravidarum. Hormonal effects on neurotransmitter function may also play a role in nausea and vomiting of pregnancy and in some vestibular disorders; however, the specific neural mechanisms of nausea and vomiting have not been identified. Until the neurochemical processes underlying these phenomena are understood, prevention and management will remain in the domain of astute, but so far limited, clinical observation.

NASA Discipline Neuroscience↗
NASA NTRS1994

Mammalian Vestibular Macular Synaptic Plasticity: Results from SLS-2 Spaceflight

The effects of exposure to microgravity were studied in rat utricular maculas collected inflight (IF, day 13), post-flight on day of orbiter landing (day 14, R+O) and after 14 days (R+ML). Controls were collected at corresponding times. The objectives were 1) to learn whether hair cell ribbon synapses counts would be higher in tissues collected in space than in tissues collected postflight during or after readaptation to Earth's gravity; and 2) to compare results with those of SLS-1. Maculas were fixed by immersion, micro-dissected, dehydrated and prepared for ultrastructural study by usual methods. Synapses were counted in 100 serial sections 150 nm thick and were located to specific hair cells in montages of every 7th section. Counts were analyzed for statistical significance using analysis of variance. Results in maculas of IF dissected rats, one 13 day control (IFC), and one R + 0 rat have been analyzed. Study of an R+ML macula is nearly completed. For type I cells, IF mean is 2.3 +/-1.6; IFC mean is 1.6 +/-1.0; R+O mean is 2.3 +/- 1.6. For type II cells, IF mean is 11.4 +/- 17.1; IFC mean is 5.5 +/-3.5; R+O mean is 10.1 +/- 7.4. The difference between IF and IFC means for type I cells is statistically significant (p less than 0.0464). For type It cells, IF compared to IFC means, p less than 0.0003; and for IFC to R+O means, p less than 0.0139. Shifts toward spheres (p less than 0.0001) and pairs (p less than 0.0139) were significant in type II cells of IF rats. The results are largely replicating findings from SLS-1 and indicate that spaceflight affects synaptic number, form and distribution, particularly in type II hair cells. The increases in synaptic number and in sphere-like ribbons are interpreted to improve synaptic efficacy, to help return afferent discharges to a more normal state. Findings indicate that a great capacity for synaptic plasticity exists in mammalian gravity sensors, and that this plasticity is more dominant in the local circuitry. The local circuit includes type II cells and is interpreted to be responsible for shaping the final output of the system.

Ross, Muriel D.D.↗
NASA NTRS2002

Influence of vestibular activation on respiration in humans

The purpose of this study was to determine the effects of the semicircular canals and otolith organs on respiration in humans. On the basis of animal studies, we hypothesized that vestibular activation would elicit a vestibulorespiratory reflex. To test this hypothesis, respiratory measures, arterial blood pressure, and heart rate were measured during engagement of semicircular canals and/or otolith organs. Dynamic upright pitch and roll (15 cycles/min), which activate the otolith organs and semicircular canals, increased respiratory rate (Delta2 +/- 1 and Delta3 +/- 1 breaths/min, respectively; P < 0.05). Dynamic yaw and lateral pitch (15 cycles/min), which activate the semicircular canals, increased respiration similarly (Delta3 +/- 1 and Delta2 +/- 1, respectively; P < 0.05). Dynamic chair rotation (15 cycles/min), which mimics dynamic yaw but eliminates neck muscle afferent, increased respiration (Delta3 +/- 1; P < 0.05) comparable to dynamic yaw (15 cycles/min). Increases in respiratory rate were graded as greater responses occurred during upright (Delta5 +/- 2 breaths/min) and lateral pitch (Delta4 +/- 1) and roll (Delta5 +/- 1) performed at 30 cycles/min. Increases in breathing frequency resulted in increases in minute ventilation during most interventions. Static head-down rotation, which activates otolith organs, did not alter respiratory rate (Delta1 +/- 1 breaths/min). Collectively, these data indicate that semicircular canals, but not otolith organs or neck muscle afferents, mediate increased ventilation in humans and support the concept that vestibular activation alters respiration in humans.

NASA Discipline Neuroscience↗